COMPARISON OF THERMOPHILIC ANAEROBIC DIGESTION PROCESSESFOR MEETING BIOSOLIDS CLASS A PATHOGEN STANDARDS

摘要

The primary objective of this study was to compare the ability of various thermophilicrnanaerobic digestion processes to disinfect sludge so that it met U.S. EPA's Class Arnpathogen requirements (40 CFR Part 503). Three thermophilic processes were assessedrnfor their ability to meet Class A requirements for fecal coliforms and pathogens: (1) twophase,rnthermophilic acid phase/mesophilic methane phase; (2) single-stage thermophilic;rnand (3) two-phase, mesophilic acid phase/thermophilic methane phase. The thermophilicrnprocesses were compared to a control (mesophilic single-stage digester). Mesophilic andrnthermophilic digesters were operated at 35℃ and 50℃, respectively. The laboratoryscalernreactors (1.5-L) were spiked with three pathogens: Salmonella, poliovirus andrnhelminth ova (Ascaris suum). All three thermophilic digesters outperformed thernmesophilic single-stage digester control in terms of fecal coliform and pathogenrndestruction. Of the three thermophilic processes, only the two-phase, mesophilic acidrnphase/thermophilic methane phase consistently achieved the Class A fecal coliform andrnpathogen reduction requirements.